Many applications require that one article, structure or item be bonded or adhered to another article, structure or item. For example, anchor bolts are employed in various fields of engineering as strengthening or reinforcing members in rock formations, or concrete or masonry structural bodies. The bolts, which are typically metallic, are inserted into holes in the rock formations, or concrete or masonry structural bodies, and are fixed or anchored therein by means of an anchor composition. Typically, the anchor composition cures or hardens (polymerizes) to form a strong bond between the rock formation, or the concrete or masonry structural body and the bolt.
It has been known to use curable synthetic resins as the primary adhesive for the safe fastening of anchoring rods, bolts and similar devices in solid rock, masonry, concrete and the like. Typically, but not exclusively, certain of the starting components of the adhesive composition are kept separate from one another and then combined at or near the point of fastening. In such so called two part systems, the components which are kept separate until the time of use are combined at the site and then introduced to the anchor bolt, the bore or hole prepared to receive the bolt, or both. Thus, the formation of the cured adhesive body that binds the fastener to the base structure is initiated at about the time the fastener is placed in its final position.
In concrete and masonry, anchor bolts are used for reinforcement. Anchor bolts are also used for attaching objects to concrete or masonry. Objects that have been attached to concrete or masonry using anchor bolts include, but are not limited to, electrical conduits, panels, piping and wall sections. Adhesive anchors are preferred over mechanical anchors for anchoring in soft concrete or masonry because adhesive anchors place less stress on the concrete or masonry. As used herein, the term “masonry” shall include, but is not limited to, stone, brick, ceramic tile, cement tile, hollow concrete block and solid concrete block.
A useful anchor composition should provide a strong bond between the concrete or masonry and the material to be anchored to the concrete or masonry, be easy to dispense at the location of use and is preferably not noxious or offensive to the user. It is also preferred that the adhesive is capable of achieving a substantial portion of its ultimate strength in a relatively short period of time. This last feature can be critically important to the commercial success of the adhesive since it can allow construction project to proceed at an efficient and profitable pace. Moreover, applicant has noted that it is desirable in many applications that the adhesive is capable of achieving good bonding properties even if it is used or applied during inclement weather or under other conditions which produce substantial moisture at the bond site.
Epoxy resins are often used as adhesives. Epoxy resins are typically one part of two-part adhesive compositions. The epoxy resin and a curing or hardening agent are typically mixed immediately prior to use, and cure within a certain amount of time. Many curing agents are nucleophilic compounds, such as amines or thiols, with at least two nucleophilic groups. Previously used amine-based curing agents often suffer from the disadvantage of producing adhesives with a relatively long cure time, particularly at relatively low temperatures. While thiol (mercaptan)-based curing agents can sometimes be formulated to react more rapidly, and at lower temperatures, than amine-based curing agents, such compounds generally produce vapors that may be noxious and/or offensive to the user's olfactory senses.